Current data indicate that serotonin plays an important role in mediating the respiratory depression produced in mice by moderate dosages of ethanol. We plan to support this data by depleting serotonin with specific drugs such as p-chlorphenylalanine or 5,6-dihydroxytryptamine. Stereotoxic lesions will be made in various diencephalic regions in an attempt to localize the site or tract responsible for the phenomenon. Studies will be done with other respiratory depressants such as opioids and barbiturates to determine specificity of serotonin-modulation in ethanol-induced depression. Behavioral tests principally loss of righting reflex will be correlated with the ability of serotonin to mediate or modulate respiratory depression. Additionally, the actions of adrenergic amines and their antagonists will be studied. Although mouse capillary blood has been used for measurements of pCO2 and pH, arterial blood from larger animals will be able to generalize our initial findings.